Polysulfide Transport Research Articles

Illuminating Polysulfide Distribution in Lithium Sulfur Batteries; Tracking Polysulfide Shuttle Using Operando Optical Fluorescence Microscopy.

High-energy-density lithium sulfur (Li-S) batteries suffer heavily from the polysulfide shuttle effect, a result of the dissolution and transport of intermediate polysulfides from the cathode, into the electrolyte, and onto the anode, leading to rapid cell degradation. If this primary mechanism of cell failure is to be overcome, the distribution, dynamics, and degree of polysulfide transport must first be understood in depth. In this work, operando optical fluorescence microscope imaging of optically accessible Li-S cells is shown to enable real-time qualitative visualization of the spatial distribution of lithium polysulfides, both within the electrolyte and porous cathode. Quantitative determinations of spatial concentration are also possible at a low enough concentration. The distribution throughout cycling is monitored, including direct observation of polysulfide shuttling to the anode and consequent dendrite formation. This was enabled through the optimization of a selective fluorescent dye, verified to fluoresce proportionally with concentration of polysulfides within Li-S cells. This ability to directly and conveniently track the spatial distribution of soluble polysulfide intermediates in Li-S battery electrolytes, while the cell operates, has the potential to have a widespread impact across the field, for example, by enabling the influence of a variety of polysulfide mitigation strategies to be assessed and optimized, including in this work the LiNO3 additive.

Regulate transportation of ions and polysulfides in all-solid-state Li-S batteries using ordered-MOF composite solid electrolyte.

A dilemma arises when striving to balance the maximum desired ion conductivity and minimize the undesired lithium polysulfide shuttling effect for all-solid-state lithium-sulfur batteries (ASSLSBs). Here, we introduce a strategy of using ordered MIL-125-NH2 as fillers for poly(ethylene oxide)-based electrolytes to simultaneously regulate the transportation of lithium ions and polysulfides. When compared to electrolytes lacking metal-organic frameworks (MOFs) and those containing disordered MOFs, the electrolyte featuring an ordered-MOF structure, denoted as three-dimensional (3D) MPPL composite solid electrolyte (CSE), exhibits the highest ion conductivity of 8.3 × 10-4 siemens per centimeter at 60°C. As a result, pouch-type ASSLSBs with 3D MPPL CSE maintains stable cycling for 400 cycles at 0.5 C at 60°C, showcasing the successful implementation of this strategy in simultaneously regulating ion and polysulfide transport. This approach opens up alternative avenues to achieve high-performance ASSLSBs with exceptional energy density.

Enhancing the Cycle Performance of Lithium-Sulfur Batteries by Coating the Separator with a Cation-Selective Polymer Layer.

Lithium-sulfur batteries are believed to possess the feasibility to power electric vehicles in the future ascribed to the competitive energy density. However, soluble polysulfides continuously shuttle between the sulfur electrode and lithium anode across the separator, which dramatically impairs the battery's capacity. Herein, the surface of a polypropylene separator (PP film) is successfully modified with a delicately designed cation-selective polymer layer to suppress the transport of polysulfides. In principle, since bis-sulfonimide anions groups on the backbone of the polymer are immobilized, only cations can pass through the polymer layer. Furthermore, plenty of ethoxy chains in the polymer can facilitate lithium-ion mobility. Consequently, in addition to obstructing the movement of negatively charged polysulfides by the electrostatic repulsive force of fixed anions, the coated multi-functional layer on the PP film also guarantees the smooth conduction of lithium ions. The investigations demonstrate that the battery with the pristine PP film only delivers 228.5 mAh g-1 after 300 cycles at 2 C with a high capacity fading rate of 60.9 %. By contrast, the polymer-coated sample can release 409.4 mAh g-1 under the identical test condition and the capacity fading rate sharply declines to 43.2 %, illustrating superior cycle performance.

An ultrathin double-layer covalent organic framework/zwitterionic microporous polymer functional separator for high-performance lithium-sulfur battery

The development of efficient lithium-sulfur (Li-S) battery depends on a well-designed functional separator that can effectively limit the transport of polysulfides while facilitating the migration of lithium ions. Herein, a multifunctional separator is fabricated with commercial polypropylene membrane (PP) as bottom porous support, a covalent organic framework (COF) film as gutter layer, and an ultrathin zwitterionic microporous polymer (QTB-SA) layer as functional barrier. In such a configuration, the COF gutter layer plays a role in adjusting the surface property of PP support without obviously increasing the transport resistance of lithium ions, while the QTB-SA functional barrier enables the formation of confined ionic channels due to its intrinsic microporosity and zwitterionic nature. Thus, selective ion transport concerning this separator can be expected owing to the availability of electrostatic interaction with lithium polysulfides. The experimental results show that the QTB-SA/COF/PP-based Li-S battery possesses high prolonged cycling behavior (capacity decay rate of 0.087 % per cycle at 1C over 500 cycles) and attractive rate capability up to 5C. Moreover, the Li-S battery can deliver a decent areal capacity of 3.4 mAh cm−2 after 100 cycles with a raised sulfur loading (4.5 mg cm−2).

Electrochemical study of the redox processes of elemental sulfur in organic solvents using poly (3,4-ethylene-dioxy-thiophene) modified glassy carbon electrodes as working electrodes and ionic liquids as electrolytes

The commercial use of Lithium-sulfur batteries has been limited by their short service life due to the shuttle effect of polysulfides, which is due to the transport of polysulfides towards the anode and the formation of highly resistive deposits that passivate the electrodes. This problem can be solved by decreasing the transport of these species from the cathode to the anode and simultaneously improving the kinetics of electron transfer reactions. This work studies by electrochemical impedance spectroscopy and cyclic and ac voltammetry the redox reactions of elemental sulfur in either acetonitrile (CH3CN) or dimethyl sulfoxide (DMSO) using as a working electrode either pristine glassy carbon (GC) or GC modified with a thin film of poly-3,4-ethylenedioxythiophene (GC-PEDOT) as working electrodes. Tetrabutylammonium hexafluorophosphate (TBAPF6), 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-Butyl-3-methylimidazolium triflate ([Bmim][OTf]) were investigated as electrolytes. It was found that the kinetics of the first reduction reaction of S8 on GC is much faster in CH3CN than in DMSO and when [Bmim][OTf] is used as an electrolyte. On the other hand, it was found that PEDOT is electrocatalytic for the first reduction reaction of elemental sulfur. Finally, by encapsulating the sulfur in PEDOT it is possible to increase the retention of the sulfur species inside PEDOT upon redox cycling if pure ionic liquids are used as electrolytes.

Hybrid Lithium Polysulfide Flow Batteries for Large Scale Energy Storage

Lithium-sulfur battery chemistry has garnered global attention as a promising next-generation energy storage technology due to its significantly higher theoretical capacity (450 Wh/kg) compared to lithium-ion (265 Wh/kg), and the fact that its elemental components are green, safe and abundant[1]. As opposed to lithium-ion, the cathode solution chemistry is rich, as elemental sulfur forms polysulfide chains during discharge which can transport and deposit on the metallic lithium anode during a dissolution-migration-deposition “shuttle” mechanism which in effect a) cause a constant internal shorting current proportional to the transport of polysulfides and b) cause a build-up of lithium- and sulfur-rich solid-electrolyte interphase (SEI) on the anode which irreversibly passivates the lithium metal anode. This effect must be supressed at all costs in conventional lithium-sulfur batteries, and is achieved by encouraging rapid precipitation of Li2S salts by the use of low-donor number solvents for the electrolyte such as diglyme (DME) and dioxolane (DOL).However, polysulfide chains (Li2Sx, 3 ≤ x ≤ 8) have great potential as redox couples due to their stable, successive multistep redox behaviour and have been successfully demonstrated in hybrid redox-flow battery configurations[2], in particular enabled by lithium nitrate as an additive to the catholyte that forms a stable SEI on the lithium metal surface that greatly reduces the polysulfide deposition. The lithium-polysulfide redox flow battery in theory far outstrips current state of the art vanadium redox flow batteries due to the higher capacity density in the catholyte (50-150 Wh/L vs 30 Wh/L), and the energy dense lithium metal[2]. However, the solubility of polysulfides decrease with chain length and depth of discharge, and high polarity, high donor number solvents that can enable high polysulfide concentrations[3] are typically far more reactive towards lithium metal[4]. Moreover lithium nitrate have little effect as anode protectant in this class of solvents compared to low donor number, low polarity solvents such as DME and DOL, and the polysulfide reduction pathway is dependent on the stabilising property of the solvent[5].In collaboration with our commercial partner StorTera under the Faraday Institute, we have developed novel techniques for catholyte analysis. We show the role of nitrate consumption rate on protection of the anode, and the relative corrosive rate of lithium in a high polarity, high donor number class solvent (DMSO) versus conventional low polarity, low donor number class solvent (DOL/DME). Further we explore avenues to protect metallic lithium in highly concentrated polysulfide catholyte that enables large-scale energy storage that surpasses lithium-ion and vanadium redox flow batteries for cost, safety, serviceability and environmental impact. Such factors will be key for commercial deployment, in particular suitable for developing countries where microgrids for remote communities rely on intermittent renewable power supply. Zhang, G., Zhang, Z. W., Peng, H. J., Huang, J. Q. & Zhang, Q. A Toolbox for Lithium–Sulfur Battery Research: Methods and Protocols. Small Methods 1, 1–32 (2017).Yang, Y., Zheng, G. & Cui, Y. A membrane-free lithium/polysulfide semi-liquid battery for large-scale energy storage. Energy Environ. Sci. 6, 1552–1558 (2013).Pan, H. et al. On the Way Toward Understanding Solution Chemistry of Lithium Polysulfides for High Energy Li-S Redox Flow Batteries. Adv. Energy Mater. 5, (2015).Gupta, A., Bhargav, A. & Manthiram, A. Highly Solvating Electrolytes for Lithium–Sulfur Batteries. Adv. Energy Mater. 9, 1–9 (2019).Lu, Y. C., He, Q. & Gasteiger, H. A. Probing the lithium-sulfur redox reactions: A rotating-ring disk electrode study. J. Phys. Chem. C 118, 5733–5741 (2014).

A saccharide-based binder for efficient polysulfide regulations in Li-S batteries

The viability of lithium-sulfur batteries as an energy storage technology depends on unlocking long-term cycle stability. Most instability stems from the release and transport of polysulfides from the cathode, which causes mossy growth on the lithium anode, leading to continuous consumption of electrolyte. Therefore, development of a durable cathode with minimal polysulfide escape is critical. Here, we present a saccharide-based binder system that has a capacity for the regulation of polysulfides due to its reducing properties. Furthermore, the binder promotes the formation of viscoelastic filaments during casting which endows the sulfur cathode with a desirable web-like microstructure. Taken together this leads to 97% sulfur utilisation with a cycle life of 1000 cycles (9 months) and capacity retention (around 700 mAh g−1 after 1000 cycles). A pouch cell prototype with a specific energy of up to 206 Wh kg−1 is produced, demonstrating the promising potential for practical applications.

High Sulfur Loading Layered Cathode and Gel Electrolyte

Lithium sulfur (Li-S) batteries are promising candidates for next-generation energy storage devices as they are capable of providing higher energy density and lower cost in comparison to the state of the art Li-ion batteries. To gain these characteristics, there are challenges such as polysulfide crossover, large volume changes during cycling, and deposition of insulating lithium sulfide that need to be alleviated. A popular approach to address these issues is to control the structure and properties of the carbon cathode in order to influence the transport of polysulfides, surface area for reaction, and lithium sulfide deposition. Using gel electrolyte is another approach that can reduce the shuttle effect and also safety concerns regarding the flammable liquid electrolyte can be reduced by deploying gel electrolyte. Towards this direction, we developed a layer-on-layer cathode structure with sulfur-impregnated activated carbon alternating with graphene layer, which was fabricated by Air-assisted electrospray. A much higher sulfur loading compared to slurry cast cathodes can be provided in this method. Combining the new cathode with gel electrolyte can offer higher safety of the battery and capacity retention.

Lithium fluoride as an efficient additive for improved electrochemical performance of Li-S batteries

To overcome the issue of the shuttle effect of the lithium-sulfur (Li-S) battery upon repeated cycle process, in this work, lithium fluoride (LiF) as a coating to form a crosslinked network structure with aramid paper (AP), which inhibits the diffusion and dissolution of polysulfides. LiF interacts with the electrolyte to form an artificial solid electrolyte interface (SEI) membrane that hinders the transport of polysulfides; The porous structure of the AP interlayer allows the LiF/CNT slurry to adhere tightly. The Li-S battery assembled with LiF/AP interlayer displayed a high discharge capacity of 885 mAh/g at 1C after 200 cycles, with a low attenuation rate of 0.0302 % per-cycle, and the specific capacity of the Li-S battery using the LiF/AP interlayer at 4C is 693 mAh/g. Our researchs are expected to introduce a new generation of high performance Li-S batteries based on a economical and effective strategy of LiF/AP composite interlayer.

Polysulfide entrapment and retardation in gel electrolyte Li–S batteries: experiments and modeling

To investigate polysulfide retardation in gel electrolyte Li–S batteries, discharge was paused near its end and then restarted. Polysulfide transport limitations were found to be responsible for reduced capacity compared to liquid systems.

A synergistic modification of polypropylene separator toward stable lithium–sulfur battery

Lithium sulfur batteries have widespread applications in many different fields ranging from electric vehicles to portable electronic devices. Design and development of advanced separators that can inhibit the polysulfide shuttling is critical for the development of lithium sulfur battery. Herein, we report a synergistic modification of polypropylene (PP) separator using multiwall carbon nanotubes loaded with CeO2 nanoparticles (MWCNTs/CeO2). Due to the high polysulfide affinity of CeO2, such a modification enables effective prevention of polysulfide transport through the separator. Besides, MWCNTs in the modification layer also block polysulfides shuttling by physical adsorption and regulate the charge transfer by function as a secondary current collector. As a result of this functional synergy, lithium sulfur battery assembled with PP- MWCNTs/CeO2 separator shows stable discharge performance with a capacity of 520.7 mAh g-1 retained after 300 cycles.

Modeling the Effect of Layer-on-Layer Cathodes in Lithium-Sulfur Batteries

Lithium sulfur (Li-S) batteries are promising candidates for next-generation energy storage due to their high theoretical energy density and environmentally abundant chemical inputs. However, well-known challenges such as polysulfide crossover, large volume changes during cycling, and deposition of insulating lithium sulfide limit the capacity and capacity retention of Li-S batteries. A popular approach to address these issues is to control the structure and properties of the carbon cathode in order to influence the transport of polysulfides, surface area for reaction, and lithium sulfide deposition. Towards this direction, we developed a layer-on-layer cathode structure with sulfur-impregnated activated carbon alternating with graphene. The layered structure exhibits improved capacity over the control at low rates but the benefits diminish at high rates and high graphene loadings. To explain this behavior, we use a 1-dimension + time numerical continuum model for the Li-S full cell which is validated against experimental data. The model includes the electrochemical reactions and precipitation of sulfur and intermediate polysulfide species, transport of species through the battery, lithium sulfide nucleation and growth, and adsorption of polysulfides. Experiments and simulations suggest that a combination mass-transfer limitations and surface passivation effects is crucial in describing the performance of the cells, and the effect of cathode properties is further investigated using the model.

“Shuttle” in Polysulfide Shuttle: Friend or Foe?

The polysulfide shuttle effect, where sulfur species reach the negative electrode surface and undergo chemical reduction, is believed to be a major bottleneck in lithium–sulfur chemistry. The importance of this phenomenon is often judged based on phenomenological arguments, which do not account for mesoscale complexations. This work presents a comprehensive investigation of the coupled interactions arising from speciation, concentrated electrolyte solution, and reaction time scales. Polysulfide transport consists of diffusion and migration, which determines the net flux. This study demonstrates that the polysulfide shuttle effect can be bounded between reaction-limited and shuttle-limited regimes, depending on the operational extremes. At high sulfur to electrolyte ratio (i.e. lean electrolyte condition), the polysulfide shuttle effect may not necessarily attribute to the cell performance limitation, believed contrarily otherwise.

ZnO Nanoparticles Anchored on a N-Doped Graphene-Coated Separator for High Performance Lithium/Sulfur Batteries

Fabrication of a nanocrystalline zinc oxide (ZnO)/nitrogen-doped graphene (NDG) composite using a novel and facile in situ sol-gel technique is demonstrated in this study. A two-dimensional nanostructured morphology with uniform ZnO nanoparticles (average diameter of 10 ± 4 nm) anchored on NDG nanosheets was observed via electron microscopy. The polar heteroatoms on the graphene sheets provided abundant sites for polysulfide absorption. More importantly, the strong chemical interaction between ZnO and polysulfides efficiently hindered the transport of polysulfides. Consequently, the lithium/sulfur (Li/S) battery with the ZnO/NDG composite-coated separator exhibited enhanced performance in terms of discharge capacity and cycling stability compared to the cell with a conventional separator. With the modified separator, the Li/S battery achieved a discharge capacity of 942 mAh·g−1 after the first cycle and exhibited a capacity retention of 90.02% after the 200th charge/discharge test at 0.1 C. These results indicate that suppression of the shuttling of polysulfides efficiently improves the performance of the Li/S battery.

Polymer Gel Electrolytes for Magnesium Batteries: Ion Transport and Electrochemical Characterization

The development of new rechargeable battery systems employing novel chemistries is imperative to meet the increasing energy storage demands of emerging technologies. Magnesium metal batteries are one attractive type of beyond lithium-ion system, due to the widespread abundance, gravimetric and volumetric charge capacity, and electrodeposition potential of magnesium. However, the electrolyte formulations that enable magnesium deposition and dissolution are few in comparison with lithium. Here we report on the ion transport and electrochemical properties of magnesium polymer gel electrolytes based crosslinked, ionomeric networks that are swelled. The nature of the solvent(s) and salt(s) of the liquid medium, and the charge density of the ionomer network, are all found to heavily influence the properties of the gel electrolyte. Magnesium polymer gel electrolytes are created by swelling the ionic networks in electrolytes containing AlCl3, MgCl2, and/or Mg(HMDS)2. Interestingly, higher ionic conductivities and higher current densities for magnesium deposition/dissolution are observed for some gel electrolytes compared to the properties of the pure liquid component. This is hypothesized to be due to the speciation of the free complex ions, which is altered by the presence of the ionic polymer network. These gels are further applied to the Mg-S system, and it is shown that the structure and charge density of the gels influence anionic polysulfide transport. Gel formulations are identified where polysulfides are preferentially rejected while complex magnesium cations are facilely transported across the gel. Structure-property correlations will be presented as found from the combination of SAXS/WAXS, diffusion, elemental analysis, and conductivity measurements. Single-ion conducting magnesium polymer electrolytes are also created by swelling the ionomeric networks in pure solvents. High ionic conductivities are achievable (> 10^-4 S/cm). However, even when these electrolytes have high magnesium conductivity and are electrochemical stable (non-passivating) against magnesium metal, no magnesium electrodeposition is induced at reasonable potentials. This is suspected to be due to the difficulty of the desolvation of Mg+2.

Mesoscale Physicochemical Interactions in Lithium–Sulfur Batteries: Progress and Perspective

The shuttle effect and poor conductivity of the discharge products are among the primary impediments and scientific challenges for lithium–sulfur batteries. The lithium–sulfur battery is a complex energy storage system, which involves multistep electrochemical reactions, insoluble polysulfide precipitation in the cathode, soluble polysulfide transport, and self-discharge caused by chemical reactions between polysulfides and Li metal anode. These phenomena happen at different length and time-scales and are difficult to be entirely gauged by experimental techniques. In this paper, we reviewed the multiscale modeling studies on lithium–sulfur batteries: (1) the atomistic simulations were employed to seek alternative materials for mitigating the shuttle effect; (2) the growth kinetics of Li2S film and corresponding surface passivation were investigated by the interfacial model based on findings from atomistic simulations; (3) the nature of Li2S2, which is the only solid intermediate product, was revealed by the density functional theory simulation; and (4) macroscale models were developed to analyze the effect of reaction kinetics, sulfur loading, and transport properties on the cell performance. The challenge for the multiscale modeling approach is translating the microscopic information from atomistic simulations and interfacial model into the meso-/macroscale model for accurately predicting the cell performance.

Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium-Ion Batteries.

Li7 La3 Zr2 O12 -based Li-rich garnets react with water and carbon dioxide in air to form a Li-ion insulating Li2 CO3 layer on the surface of the garnet particles, which results in a large interfacial resistance for Li-ion transfer. Here, we introduce LiF to garnet Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT-2 wt % LiF (LLZT-2LiF) has less Li2 CO3 on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic-liquid electrolytes. An all-solid-state Li/polymer/LLZT-2LiF/LiFePO4 battery has a high Coulombic efficiency and long cycle life; a Li-S cell with the LLZT-2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li-metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.

Enhancing the Stability of Sulfur Cathodes in Li–S Cells via in Situ Formation of a Solid Electrolyte Layer

Enhancing the performance of rechargeable lithium (Li)–sulfur (S) batteries is one of most popular topics in a battery field because of their low cost and high specific energy. However, S experiences dissolution during its electrochemical reactions; hence, maintaining its initial capacity is challenging. Protecting the S cathode with a Li ion conducting layer that acts as a barrier for polysulfide transport is an attractive strategy, but formation of such protective layers typically involves significant effort and cost. Here, we report a facile route to form a conformal solid electrolyte layer on S cathodes in situ using a carbonate solvent. The chemically and mechanically stable and Li ion conducting protective layer is formed by inducing electrolyte reduction and polymerization reactions on the cathode surface. The layer serves as a polysulfide’s barrier, successfully helping to retain S active material in the carbon pores. In addition, it helps to improve the performance of Li anodes.

Polysulfide transport through separators measured by a linear voltage sweep method

Shuttle of polysulfide from the sulfur cathode to lithium metal anode in rechargeable lithium–sulfur batteries is a critical issue hindering cycling efficiency and life. Several approaches have been developed to minimize it including polysulfide-blocking separators; there is a need for measuring polysulfide transport through separators. We here show a linear voltage sweep method to measure anodic (oxidization) current of polysulfide crossed separators, which can be used as a quantitative measurement of the polysulfide transport. The electrochemical oxidation of polysulfide is diffusion controlled. The electrical charge in Coulombs produced by the oxidation of polysulfide is linearly related to the concentration of polysulfide within a certain range (≤0.5 M). Separators with a high porosity (large pore size) show high anodic currents, resulting in fast capacity degradation and low Coulombic efficiencies in Li–S cells. These results demonstrate this method can be used to correlate the polysulfide transport through separators with the separator structure and battery performance, therefore provide guidance for developing new separators for lithium–sulfur batteries.

Novel Heterostructures for Lithium-Sulfur Batteries

IntroductionLithium-ion batteries with their unique high voltage, high energy density chemistries have come to fruition decades of fundamental research conducted in electrochemical systems and materials. The development of a number of plug-in hybrid and fully electric vehicles (EV) using lithium-ion technology and their favorable market response is the harbinger of a long-awaited transition in automotive technology. Despite these advances, there is still a genuine need for increasing energy densities for the successful transition to EVs (1, 2). Advances in lithium-ion anode technology have made it possible to obtain ~1500 mAh/g anodes with superior cycle life (3-5). However, cathode research has been rather stymied in contrast on account of the challenges faced in designing stable, conductive materials with high capacities. Cathode capacities thus far have been limited to ~ 300 mAh/g in high voltage (1, 6) lithium manganese-nickel-cobalt oxide chemistries. Lithium sulfur and lithium-air batteries though well-known but challenging to execute, hold much more promise of matching anode capacities on account of their theoretical capacities of 2567 and 3505 Wh/kg respectively(2). The dissolution of sulfur through the formation of soluble polysulfides and the poor electronic conductivity of sulfur are however, major problems hindering Li-S batteries.It has previously been demonstrated that the use of highly conductive porous carbon matrix and carbon nanotubes can help circumvent these issues (7-10). In addition, the use of a carbon matte as a barrier layer to polysulfide transport has been demonstrated to be effective in retaining high capacity(11). There is however a need to translate this design into thick electrodes capable of delivering high overall electrode capacity. In this study, we coat pristine sulfur particles with carbon and an ionically conducting matrix using a simple chemical method. The thick electrodes were prepared using this procedure and were tested in 2025 coin cells with lithium counter/reference electrodes. We demonstrate excellent charge storage behavior of these composite electrodes at various charge-discharge rates. Extended cycling of these composite electrodes reveals much improved capacity retention. Figure 1 shows the electrochemical results of these different configurations. Results of these studies will be presented and discussed.